This invention is concerned with preparing a cooked extruded flour-based product. More particularly with extruding a flour-based dough under conditions which are effective to prepare a product with a texture, cohesiveness, appearance and rehydration characteristics of a fully baked flour-based product.
Flour-based products, that is bread, cereals, pet foods, etc., have been prepared by conventional processes to obtain specific desired textural attributes. Bread and bread particles made therefrom are generally produced by baking bread according to conventional yeast leavening procedures which involve developing dough in a mixer and development trowel, either utilizing the sponge, continuous or straight dough method (e.g. fermenting and degassing), dividing the dough, balling, intermediate proofing, sheeting, panning the dough, and having a final additional pan proofing and then baking at temperatures generally on the order of 350.degree. to 400.degree. F. (175.degree. to 205.degree. C.) wherein additional development of the dough takes place by action of the yeast (oven spring). Thereafter, the bread may be sliced, staled and diced if bread particles, croutons, or crumbs are desired. The conventional baking process results in a desireable spongy, cohesive texture which readily rehydrates upon contact with liquid. Also the baked bread has a set protein matrix wherein the starch granules are substantially swollen and intact giving it desireable textural and mouthfeel attributes. A key limitation of the baking process is that it is basically a time consuming batch cooking process thereby limiting the throughput, as well as being capital and space intensive.
Cereals and pet foods have been processed in continuous cooking-extrusion apparatus, but heretofore obtaining a baked texture, as obtained with baked bread, in such a cooking-extrusion processes has not been observed. The puffed cereal and pet food extrusion processes generally involve high temperature, pressure and shear with the extrudate being puffed by the release of steam upon exiting the extruder, resulting in a high degree of protein denaturization disrupting the protein matrix, as well as a high degree of rupturing of the starch granules. The result of this cooking-extrusion process is a plastic extrudate which generally has a low density, and is mushy, sticky and falls apart when contacted with liquid. While extruder mixing or kneading devices have been used in the industry, as well as extruder-mixing apparatus which inject gas, as in U.S. Pat. No. 4,218,480, the use of an extruder-cooker under proper conditions to prepare a fully cooked flour based product with the texture, rehydration characteristics, cohesiveness and appearance characteristics and aerated structure of a fully baked flour-based product has not been observed.
Further, the baking and cooking-extrusion processes have been limited in the amounts of heat sensitive ingredients, shear sensitive ingredients or food particles which can be incorporated while still maintaining the functionality and integrity of the ingredients and/or obtaining the desired cell structure and resultant textural attributes in the resultant product.
Thus, it is a feature of this invention to prepare a fully cooked, flour-based product with the textural attributes of a fully baked flour-based product.
It is a further feature of this invention to provide a continuous cooking-extrusion process which fully cooks a four-based dough, but without substantial disruption of the protein matrix and starch granules of the dough.
It is a further feature of this invention to provide low temperature, gentle processing of a flour-based product which will enable the incorporation of ingredients which are sensitive to high shear and high temperatures.